Especially plug connections with a low number of pins, but also coupler plugs in the form of a lambda probe must be coupled via a coupler plug. To ensure that, first of all, the plug connection is implemented correctly, a variety of securing elements are already known. Secondly, securing elements that ensure that an entire plug connection, once it has been established, cannot be released easily, are also known from the related art. The latter may be subdivided into safety mechanisms that must first be destroyed to reverse the plug connection and those in which the securing element must actively be removed so as to likewise release a plug connection.